GM Service Manual Online
For 1990-2009 cars only

Important: The battery must be fully charged and serviceable.

Electrical Information Reference

    •  Diagnostic System Check - Vehicle.
    •  Circuit Testing.
    •  Wiring Repairs.
    •  Battery Inspection/Test.
    •  Battery Electrical Drain/Parasitic Load Test.

    Caution: Refer to Safety Glasses Caution in the Preface section.

  1. Ignition OFF, disconnect the battery ground cable from the battery. Refer to Battery Negative Cable Disconnection and Connection.

  2. Object Number: 1957163  Size: MF
  3. Disconnect the battery positive lead from the rear of the alternator.
  4. Important:  Insulate the terminal on the battery positive lead to prevent contact with the vehicle.

  5. Connect a DMM (2) set on amps between the battery positive lead (4) and the alternator positive post (5).
  6. Connect a DMM (1) set on volts to the alternator positive terminal (6) and a known ground.
  7. Connect the negative battery cable to the battery Refer to Battery Negative Cable Disconnection and Connection.
  8. Record the voltage reading on the DMM (1). Connect a suitable loading device to the battery positive and negative posts (3).
  9. Connect a scan tool and start the engine.
  10. While observing the scan tool, increase the engine speed to 1300 RPM
  11. Observe the DMM (2), the amperage should be 5.0-10 amps and the DMM (1) voltage should read between 13.8-15.4 volts.
  12. While observing the scan tool, increase the engine speed to 1900 RPM.
  13. Observe the DMM (2) adjust the loading device to 90 percent of the alternators maximum output.
  14. Observe the DMM (1) voltage should read between 13.8-15.4 volts.
  15. Adjust the loading device until the DMM (1) reads 13.5 volts.
  16. Observe the DMM (2) the amperage should read maximum output of alternator.
  17. Stop the engine.
  18. Disconnect the battery ground cable from the battery. Refer to Battery Negative Cable Disconnection and Connection.
  19. Disconnect both DMM's
  20. Connect the positive lead to the rear of the alternator.
  21. Remove the loading device.
  22. Connect the battery negative cable to the battery. Refer to Battery Negative Cable Disconnection and Connection.